As global living standards and urban populations continue to rise, there's a concurrent increase in the amount of waste generated. Waste management has become the single largest expenditure for most municipalities. Ineffective management of waste is posing serious risk of rapid deterioration in levels of sanitation and general quality of urban life.
Disposal of wastes is commonly done by dumping (on land or into water bodies), incineration, and/or long term storage in a secured facility. All these methods have varying degrees of negative environmental impacts with adverse health risks if not properly executed. Apart from these methods, recycling, composting, recovery (including resource and energy), and biological reprocessing etc. are emerging as acceptable sustainable modes of waste management. In recycling, materials generally undergo a chemical transformation and resultant products are recycled to be used for various purposes. For the purpose of resource recovery the organic waste is preferably anaerobically digested (also called Anaerobic Composting or Biomethanation) as compared to aerobic digestion to obtain compost which can be used as an organic fertilizer on agricultural fields. Anaerobic digestion of organic waste results in energy in the form of biogas, and compost in the form of a liquid residual. The biogas consists of methane and carbon dioxide and can be used as fuel or, by using a generator, it can be converted to electricity on-site. This reduces greenhouse gas emissions by using methane as an energy source which would otherwise be emitted from landfilling waste. Landfilling waste gas is similar in composition to biogas with lower amount of methane and differences in component gases. However, the conversion of biogas to electricity is not economically attractive and also results in significant loss of energy during conversion.
Methane, present in biogas or landfill gas, can also be converted to syngas and then to chemicals such as methanol. This gas to liquid conversion happens at high temperature and pressure necessitating huge capital investments.
Efficient utilization of biogas as well as methane has always been a challenging task. Advances in biotechnology are enabling development of new and improved microorganisms for efficient conversion of biomass to useful products. However, the existing state of the art does not provide for a unified and efficient way of converting organic wastes and more specifically biogas or methane to target chemicals by employing recombinant microorganisms.